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Tip revision: bad9a580caaba5088bea569c9c6775dab12b8103 authored by Benjamin Peterson on 14 April 2018, 22:06:30 UTC
2.7.15rc1 version bump
2.7.15rc1 version bump
Tip revision: bad9a58
weakref.rst
.. highlightlang:: c
.. _weakrefobjects:
Weak Reference Objects
----------------------
Python supports *weak references* as first-class objects. There are two
specific object types which directly implement weak references. The first is a
simple reference object, and the second acts as a proxy for the original object
as much as it can.
.. c:function:: int PyWeakref_Check(ob)
Return true if *ob* is either a reference or proxy object.
.. versionadded:: 2.2
.. c:function:: int PyWeakref_CheckRef(ob)
Return true if *ob* is a reference object.
.. versionadded:: 2.2
.. c:function:: int PyWeakref_CheckProxy(ob)
Return true if *ob* is a proxy object.
.. versionadded:: 2.2
.. c:function:: PyObject* PyWeakref_NewRef(PyObject *ob, PyObject *callback)
Return a weak reference object for the object *ob*. This will always return
a new reference, but is not guaranteed to create a new object; an existing
reference object may be returned. The second parameter, *callback*, can be a
callable object that receives notification when *ob* is garbage collected; it
should accept a single parameter, which will be the weak reference object
itself. *callback* may also be ``None`` or *NULL*. If *ob* is not a
weakly-referencable object, or if *callback* is not callable, ``None``, or
*NULL*, this will return *NULL* and raise :exc:`TypeError`.
.. versionadded:: 2.2
.. c:function:: PyObject* PyWeakref_NewProxy(PyObject *ob, PyObject *callback)
Return a weak reference proxy object for the object *ob*. This will always
return a new reference, but is not guaranteed to create a new object; an
existing proxy object may be returned. The second parameter, *callback*, can
be a callable object that receives notification when *ob* is garbage
collected; it should accept a single parameter, which will be the weak
reference object itself. *callback* may also be ``None`` or *NULL*. If *ob*
is not a weakly-referencable object, or if *callback* is not callable,
``None``, or *NULL*, this will return *NULL* and raise :exc:`TypeError`.
.. versionadded:: 2.2
.. c:function:: PyObject* PyWeakref_GetObject(PyObject *ref)
Return the referenced object from a weak reference, *ref*. If the referent is
no longer live, returns :const:`Py_None`.
.. versionadded:: 2.2
.. warning::
This function returns a **borrowed reference** to the referenced object.
This means that you should always call :c:func:`Py_INCREF` on the object
except if you know that it cannot be destroyed while you are still
using it.
.. c:function:: PyObject* PyWeakref_GET_OBJECT(PyObject *ref)
Similar to :c:func:`PyWeakref_GetObject`, but implemented as a macro that does no
error checking.
.. versionadded:: 2.2